I'm not overweight. I fit comfortably in an airline seat. OK comfortably may be pushing it. Airlines restricted the recline when the added more seats but sometimes it wasn't done right or is broken. Can be an issue when the passenger in the seat in front of you reclines.
That said there are two different points of view.
1) The passenger is buying a seat to travel from airport A to airport B. A passenger who is too big to sit in said seat is required to purchase a second seat. This sounds fair too most of us. One question. What happens if an airline decides to further reduce the width of seats so that just under half of all passengers need to purchase a second seat? That means the seat won't be comfortable for passengers who "just fit". Could an airline get away with that? Maybe Spirit. Oh you want a sit big enough to actually use? Our new airline configuration gives us extra seats to sell. Just let us know when you book how many extra seats you think you'll need.
2) The passenger is purchasing transportation from airport A to airport B. It's up to the airline to decide how to accommodate larger passengers, without charging them extra. Block an empty middle seat. Move the passenger to first class or move another passenger to free up a seat. What other business makes an overweight customer pay extra? Some venues (sporting arenas, movie theaters) have seats without arms or a place where wheelchair customers can be accommodated. They can put a folding chair in such a location. Seat guru will tell you the last row, or the last row of seats in a section, are often poor. The seat doesn't recline, the seat in front of you does recline and the pitch isn't increased. I got stuck with one such seat and it was worse. They needed a wider aisle at that spot so the seat was slightly narrower then other seats. No reason why an airline couldn't attempt to compensate by putting 2 seats instead of 3 in that aisle.
US airlines, and most of us, take the point of view. Canada takes the second.
edited to add: Vacationclub. It's never a good idea to publicly question the actions of a moderator. Send a PM if you have a question. You might, or might not, get an answer. It's against the rules in every internet board where I actually read the rules. You don't know what posts were edited or deleted. Sometimes a different person will read the same post a different way. What isn't fat bashing (pick the issue) to you might be read as that by someone else. I don't recall seeing any posts in this thread so egregious as to motivate me to take the, very rare, action of using the report this post icon.
Goofy4tink doesn't do a lot of "heavy" moderating. Either there were posts edited or people might read some of the posts differently then the way you or I read them.